If this has been posted elsewhere then forgive me, I did a search, as I had the problem myself and I didnt find anything.

For those of you who have been having strange issues with artwork, more specifically with syncing to ipod/iphone. In my case I ended up with black squares for some artwork, incorrect artwork for others, not just on music, but videos and audiobooks too. It was all showing correctly in iTunes, and I tried loads of different ways to try and fix it, all to no avail.